The correct answer is B. An allograft, also called a homograft, is a temporary skin graft often used as temporary coverage for extensive burns or wounds to provide a protective barrier and promote healing. They are eventually replaced by the patient's own skin as the graft is slowly reabsorbed. Allografts involve using skin tissue obtained from another human donor. This can be from a deceased person or from living donors in certain circumstances. 

The term "donor site" refers to the area from which the skin is taken for transplantation, while the area where the skin is transplanted is referred to as the "recipient site."

Xenografts involve using skin tissue from animals, typically pigs, as a temporary covering for wounds. Similar to allografts, xenografts serve as a temporary protective layer while the patient's own skin regenerates and heals. Xenografts are also eventually reabsorbed by the body.

It's important to note that allografts and xenografts are considered temporary measures, and the ultimate goal is to replace them with the patient's own skin through procedures such as autografts (using the patient's own skin) or other reconstructive techniques. Autografts are the most common type of skin graft.